rocketgeek101's Mid-Power Scratch Build -- Firelight

[rocketgeek101]

Hello!

This is the build thread for my first mid-power scratch build. The rocket will feature aerofoiled surface mount fins made from 0.6cm thick plywood, a 29mm motor mount, and for motor retention; I will be using an Estes Pro Series 2 retainer. The nose cone will be an LOC 54mm nose cone.

The body tube is the tube from a roll of plastic sheet. It is very strong. The OD of the tube is about 5.7cm making it very close in size to 54mm body tubes.

So far I have made the fins and attached them to the body tube. The motor mount hasn't been made yet as I'm waiting for some parts to arrive in the mail.

I've attached a PDF showing the design of the rocket.

Pic 1: Aerofoiling the fins

Pic 2: The completed fin

Pic 3: All three fins completed

Pic 4: Tacking the fins onto the body tube (I used Weldbond for this)

View attachment Scratch29.pdf

 

[rocketgeek101]

Another pic: Epoxy fillets applied.

 

[T-Rex]

I'm curious why you didn't slot the tube and go through the wall with your fins?

 

[rocketgeek101]

I'm curious why you didn't slot the tube and go through the wall with your fins?

The main reason was for simplicity. I didn't want to have to deal with cutting slots in the tube and adding tabs to the fins. Another reason is that the fin design is such that there is a reduced chance of the fins being damaged upon landing (I felt that with this fin design TTW fins would be overkill and just add extra weight to the rear of the rocket).
And thirdly, I wanted to get some experience surface mounting fins on a higher powered rocket; in preparation for some minimum diameter projects I would like to do someday.

 

[T-Rex]

OK, as I said, just curious. I've gotten to where I slot everything, but then I haven't attempted a minimum diameter yet either. Maybe I'm making extra work for myself.

 

[rocketgeek101]

So I've run into a bit of a snag: My epoxy fillets wont seem to fully cure. I can easily make little marks in them using my fingernail. I wouldn't worry about it if the fins were TTW, but they are not. Is there any way to make the epoxy fully harden? The epoxy resin was thicker then it should of been, but I just figured that was because I stored the epoxy in my basement, which is on the cool side. I think I mixed it 50/50, though I just eyeballed it so I cant be 100% sure. The epoxy I used is Mercury Adhesive 15min epoxy.

Any advise? Would it most likely be strong enough as is, or maybe I should start over?

 

[CarVac]

Not all epoxy, especially fast curing ones, hardens fully.

 

[rocketgeek101]

Had some time to work on this one again!

I haven't glued the Motor mount in yet. All that you see in the pics is dry fitted.

rg101

 

[Aksrockets]

Looks good but I'm hoping that tape it only temporary.

Alex

 

[jpummil]

Had some time to work on this one again!

I haven't glued the Motor mount in yet. All that you see in the pics is dry fitted.

rg101

So, what ever happened with the epoxy? Still a bit soft, or did it harden over the course of a month?

 

[rocketgeek101]

Looks good but I'm hoping that tape it only temporary.

Alex

Unfortunately the tape isn't temporary, I needed to build up the OD of the tube to match the OD of the nose cone. With some filler and a lot of sanding it will look decent.

So, what ever happened with the epoxy? Still a bit soft, or did it harden over the course of a month?

The epoxy did harden...it just took a VERY long time to.

 

[thobin]

When I need to build up a tube I use brown paper bags. (brown paper can be found at some mail and shipping stores on a roll, this works the best.) Glue it on with some white glue, a nice thin coat on both paper and tube you can even water it down a bit to increase your build time. And you will only have one seam to deal with. Masking tape will have a bit of flexibility that might chip the paint.

TA

 

[rocketgeek101]

When I need to build up a tube I use brown paper bags. (brown paper can be found at some mail and shipping stores on a roll, this works the best.) Glue it on with some white glue, a nice thin coat on both paper and tube you can even water it down a bit to increase your build time. And you will only have one seam to deal with. Masking tape will have a bit of flexibility that might chip the paint.

TA

That's a good suggestion, but for this build I will stick with the tape as I've already put it on and am happy with the results.

 

[rocketgeek101]

What about if I coat the tape with a thin film of glue? would that help?

Thanks,

Rocketgeek101

 

[thobin]

It might, the problem is the adhesive on the tape it just adds a bit of flexibility to it, and the more layers that you put the greater its going to flex. Just push your thumb on your roll of tape and feel how much it moves. If you can get the glue to soak all the way through and harden all the layers it should work? IDK I may be up in the night, tape just has to much flex for my liking.



TA

 

[cjp]

Very nice so far,have you put it on a scale?The fins look thick,but that's not a bad thing.You might on your next build get some Baltic Birch plywood.Mybe 1/8".I like the looks of your design,should really move off the pad.What motor were you thinking of using?

 

[garmtn]

just sent a friend pics of my "Trident" scratch built. "Trident" in my album for "garmtn"

 

[cwbullet]

Very nice bevels on the fins. Post some pics and videos of the first flight.

 

[rocketgeek101]

Thanks for all the comments so far! I've made a little more progress on her: More even layer of tape applied (looks real nice if I do say so myself). Tomorrow I might add a thin coat of glue on the tape in the hopes of it helping the tape from flexing (assuming it will flex).

The batteries in my scale are dead at the moment so I don't have an exact weight. Hopefully tomorrow I'll be able to go buy some batteries for it.

Yes the fins are thick - I really dig the looks of thick beveled fins (and that's the only thickness of plywood I had on hand )

cwbullet: you might have already seen this, but if you look at my first post; you'll see a pic of how I beveled the fins. I came up with that idea myself. It works very well.

I have no ideas at the moment for what motor to fly her on. I'm waiting to get an accurate weight before I start planing on what motor to use. All I know is that it will be a Pro-29 load.

thanks for looking,

rocketgeek101

 

[rocketgeek101]

Covered the tape in a thin layer of glue. It seems to have done the trick. The tape is VERY stiff and feels quite strong.

more pics coming soon.

 

[rocketgeek101]

What size parachute should I use? I think I could use one thats on the small side, as the fins are pretty far up the BT. Still haven't bought batteries for the scale; so no weight yet.

 

[soxfan121]

What size parachute should I use? I think I could use one thats on the small side, as the fins are pretty far up the BT. Still haven't bought batteries for the scale; so no weight yet.

maybe a 12in. parachute with 3-4 ft of shock cord. I have a question also, i've always used aluminum tube for my launch lugs, which is better the button style or the tube style? Or is it just a matter of what launch pad you plan on using?

 

[rocketgeek101]

Alright,

I've sanded the tape smooth. The tape idea worked out very well in the end. It will only require a bit of filling to get it perfect.


I also realized that I never posted how I did the nose cone. The cone is an LOC 54mm nose cone with the shoulder cut off an replaced with a home made coupler and bulkhead.

Thank for looking, more details to follow soon.

 

[rocketgeek101]

Here is a pic of my MPR fleet. This also gives you a good idea as to the scale of this build.

 

[rocketgeek101]

First round of filler complete

 

[rocketgeek101]

Second coat of filler applied.

 

[rocketgeek101]

I sanded the filler smooth. It came out pretty well. I will have to touch up the fin fillets a bit, and possibly apply a 3rd coat on the tape.

You guys got any name suggestions?

More coming soon!

rg101

 

[86mustang408w]

What brand of filler do you use? I've never really used filler before, just trying to get some ideas.

 

[rocketgeek101]

What brand of filler do you use? I've never really used filler before, just trying to get some ideas.

I used this stuff:

 

[rocketgeek101]

I'm curious, has anybody been following this thread? Is it worth my effort to continue? I don't seem to get that many replies...